Pre-cast pervious concrete

ABSTRACT

A pervious concrete slab is pre-cast in a reusable mold or form to define at least one keyway configured and arranged to engage with a complementary keyway of another similar pre-cast pervious concrete slab. The concrete slab is then cured in a controlled environment, transported to an installation site, and installed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/188,648,filed Jul. 22, 2011, which application claims the benefit of provisionalapplication Ser. No. 61/367,408, filed Jul. 24, 2010, which applicationsare incorporated herein by reference in their entirety.

BACKGROUND

Pervious concrete is a type of concrete with sufficient porosity toallow water from precipitation and other sources to pass directlytherethrough. Example applications for pervious concrete includereducing runoff from a site and allowing groundwater recharge. However,pervious concrete is typically poured in situ, and thus quality of theconcrete may be impacted by prevailing ambient conditions.

SUMMARY

In one aspect, a pre-cast pervious concrete slab is disclosed. Thepre-cast pervious slab includes a body composed of a combination ofaggregate particles, cementitious materials, and water, and wherein thebody includes a void content of about 10% to about 30%.

In another aspect, a water filtration system is disclosed. The waterfiltration system includes a plurality of pervious concrete pavers, eachcomposed of a combination of aggregate particles, cementitiousmaterials, and water, and including a void content of about 10% to about30%; and a filtration layer positioned beneath the plurality of perviousconcrete pavers within the ground surface.

In yet another aspect, a method of forming a pre-cast pervious concreteslab for a water filtration system is disclosed. The method includes:forming a mixture comprising aggregate particles, hydraulic cement, andwater; pouring the mixture into a mold to define the pervious concreteslab; vibrating the mixture within the mold for a first predeterminedtime period, wherein a frequency of the vibration is in a range of about10 Hz to about 1000 Hz; compressing the mixture within the mold for asecond predetermined time period, wherein a pressure of the compressionis in a range of about 10 psi to about 1000 psi; and releasing thepervious concrete slab from the mold following the second predeterminedtime period.

This Summary is provided to introduce a selection of concepts, in asimplified form, that are further described below in the DetailedDescription. This Summary is not intended to be used in any way to limitthe scope of the claimed subject matter. Rather, the claimed subjectmatter is defined by the language set forth in the Claims of the presentdisclosure.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of a first example water filtrationsystem.

FIG. 2 shows a side view of an example pervious concrete slab having atwo-sided keyway system.

FIG. 3 shows a top view of a pervious concrete slab having a two-sidedkeyway system.

FIG. 4 shows a side view of an example pervious concrete slab having afour-sided keyway system.

FIG. 5 shows a top view of a pervious concrete slab having a four -sidedkeyway system.

FIG. 6 shows a top view of an example installations site.

FIG. 7 shows a cross-sectional view of a second example water filtrationsystem.

FIG. 8 shows an example method for forming a pre-cast pervious concreteslab.

DETAILED DESCRIPTION

The present disclosure is directed towards a pre-cast pervious concretesystem and method. In one example embodiment, a pervious concrete slabis pre-cast to define at least one keyway configured and arranged toengage with a complementary keyway of another similar pre-cast perviousconcrete slab. In the example embodiment, the term “pre-cast” refers toa form of construction where concrete is cast in a reusable mold orform. The concrete is then cured in a controlled environment,transported to an installation site, and lifted into place. Although notso limited, an appreciation of the various aspects of the presentdisclosure will be gained through a discussion of the examples providedbelow.

Referring now to FIG. 1, a cross-sectional view of a first example waterfiltration system 100 is shown in accordance with the presentdisclosure. The water filtration system 100 includes a first paver 102and a second paver 104, each at least partially positioned within aground surface 106 of an installation site 108. Examples of aninstallation site include a parking lot, driveway, sidewalk, patio, pooldeck, and others.

As described in detail below in connection with FIGS. 2-8, the firstpaver 102 and the second paver 104 are pre-cast pervious concrete slabshaving complementary features that engage each other for bonding thefirst paver 102 and the second paver 104 to one another.

The water filtration system 100 also includes an aggregate layer 110, afirst fabric layer 112, a subgrade layer 114, and a second fabric layer116.

The aggregate layer 110 is a filtration layer at least partiallypositioned within a soil layer 118 beneath the first paver 102 and thesecond paver 104. In one embodiment, the aggregate layer 110 is formedof stone or rock particles having an average particle size of about ⅜inches, or about 9.5 millimeters. Other embodiments are possible. Forexample, composition and/or size of particulates within the aggregatelayer 110 may be selectively chosen based on composition of soils (e.g.,sand, clay, combinations thereof, etc.) relatively near the aggregatelayer 110. Additionally, a depth of the aggregate layer 110 may beselectively chosen based on composition of soils relatively near theaggregate layer 110 and/or cost associated with depositing the aggregatelayer 110.

The first fabric layer 112 is positioned between the aggregate layer 110and the subgrade layer 114. In one embodiment, the first fabric layer112 is a woven or non-woven filter fabric that functions to minimize thetransfer of contamination and/or particles from the subgrade layer 114into the aggregate layer 110, which may cause clogging or reduction indrainage capacity of the aggregate layer 110. Other embodiments arepossible.

The subgrade layer 114 is a filtration layer at least partiallypositioned in a subsoil layer 120 beneath the first fabric layer 112. Inone embodiment, the subgrade layer 114 is formed of a construction sand.Other embodiments are possible. For example, composition and/or size ofparticulates within subgrade layer 114 may be selectively chosen basedon composition of soils relatively near the subgrade layer 114.Additionally, a depth of subgrade layer 114 may be selectively chosenbased on composition of soils relatively near the subgrade layer 114and/or cost associated with depositing the subgrade layer 114.

The second fabric layer 116 generally encapsulates or surroundsrespective portions of the first paver 102, second paver 104, aggregatelayer 110, and subgrade layer 114 that are exposed to the soil layer 118and/or the subsoil layer 120. In one embodiment, the second fabric layer116 is a woven or non-woven filter fabric that functions to minimize thetransfer of contamination and/or particles from the soil layer 118 andsubsoil layer 120 into the first paver 102, second paver 104, aggregatelayer 110, first fabric layer 112, and subgrade layer 114, which maycause clogging or reduction in drainage capacity of the same. The secondfabric layer 116 further increases stability of the system as a whole.Other embodiments are possible.

The first paver 102, second paver 104, aggregate layer 110, first fabriclayer 112, subgrade layer 114, and second fabric layer 116 together forma water filtration system.

For example, when water 122 from precipitation or other sources isincident upon respective exposed portions 124, 126 of the first andsecond paver 102, 104, the water 122 passes through and is filtered bythe first and second paver 102, 104, aggregate layer 110, first fabriclayer 112, and subgrade layer 114, and subsequently percolates into thesubsoil layer 120. The second fabric layer 116 generally preventscontamination of filtered water as it passes through the first andsecond paver 102, 104, and respective layers 110, 112, and 114. Otherembodiments are possible. For example, in some embodiments, one or moreof the first fabric layer 112, subgrade layer 114, and second fabriclayer 116 are omitted from the system. Still other embodiments arepossible.

In some embodiments, a perforated pipe 128 is positioned beneath thesubgrade layer 114 and the second fabric layer 116 to capture at least aportion of the water 122 percolating into the subsoil layer 120 as partof a water recycling system. In the example embodiment, the perforatedpipe 128 is coupled to a first non-perforated pipe 130, which in turn iscoupled to an inlet 132 of a storage tank 134. Water 122 within thestorage tank 134 may then be transferred to a disbursement mechanism 136(e.g., sprinkler, container, etc.) protruding from the ground surface106 via a second non-perforated pipe 138 coupled to an outlet 140 of thestorage tank 134.

Referring now to FIGS. 2 and 3, the first paver 102 and the second paver104 of FIG. 1 are shown in detail. FIG. 2 shows a side view of the firstpaver 102 and the second paver 104. FIG. 3 shows a top view of the firstpaver 102.

The first paver 102 and the second paver 104 are pervious concreteslabs, each including a body 200 generally composed of a combination ofaggregate particles, cementitious materials, and water. An examplemethod of forming the first paver 102 and the second paver 104 isdescribed in detail below in connection with FIG. 8.

In one embodiment, a first keyway 202 is formed or disposed along afirst edge 204 of the body 200, and a second keyway 206 is formed alonga second edge 208 of the body 200 opposite the first edge 204. The firstkeyway 202 and the second keyway 206 each have a thickness 210 that isless than a maximum thickness 212 of the body 200. In one embodiment,the maximum thickness 212 of the body 200 is in the range of about 2inches to about 16 inches, or about 50 millimeters to about 406millimeters. Other embodiments are possible.

In the example shown, the second paver 104 is positioned to the firstpaver 102 such that a first keyway surface 214 of the first keyway 202of the second paver 104 is engaged to a second keyway surface 216 of thesecond keyway 206 of the first paver 102. The first keyway 202 and thesecond keyway 206 are asymmetric at least in that a first normal 217 ofthe first keyway surface 214 is orientated in a direction approximatelyopposite to a second normal 219 of the second keyway surface 216.

In example embodiments, grout (not shown) may be applied to a gap 218(see FIG. 2) to bond or connect the first paver 102 and the second paver104. In some embodiments, an adhesive may be applied to the first keywaysurface 214 and/or the second keyway surface 216 to strengthen the bondor connection between the first paver 102 and the second paver 104.Other embodiments are possible.

A channel 220 is formed within the body 200 between a third edge 222 ofthe body 200 and a fourth edge 224 of the body 200 opposite the thirdedge 222. In one embodiment, the channel 220 is about ⅜ inches in depthand about 2 inches in width, or about 9.5 millimeters in depth and about50 millimeters in width. Other embodiments are possible. For example, insome embodiments, multiple channels are formed within the body 200,depending on overall dimensions (e.g., 4′×4′×6″, 3′×4′×4″, etc.) of thebody 200. Still other embodiments are possible.

A first beveled surface 226 is formed on a first channel end 228 of thechannel 220, and a second beveled surface 230 is formed on a secondchannel end 232 opposite the first channel end 228. In practice, a strap(not shown) coupled to a lifting mechanism (not shown) is positionedinto the channel 220 to facilitate lifting and/or moving of the firstpaver 102 and the second paver 104. The first beveled surface 226 andthe second beveled surface 230 provide stress relief to the strap andfacilitate strap removal when the first paver 102 and the second paver104 are positioned in contact with the ground surface 106, or theaggregate layer 110.

The first paver 102 and the second paver 104 as shown in FIGS. 2 and 3are an example of a two-sided keyway system. Other embodiments arepossible. For example, in some embodiments, the first paver 102 and thesecond paver 104 are respectively manufactured such as to omit at leastone of the first keyway 202 and the second keyway 206. In otherembodiments, at least one of the first keyway 202 and the second keyway206 are removed (e.g., via cutting) prior to installation of the firstpaver 102 and the second paver 104. These examples correspond to aone-sided keyway system. Still other embodiments are possible.

For example, referring now to FIGS. 4 and 5, a paver 400 is shown havinga four-sided keyway system. FIG. 4 shows a side view of the paver 400.FIG. 5 shows a top view of the paver 400. In general, the paver 400 maybe used in a grid of pavers (i.e., 3×3, 3×4, etc.) in which it isdesirable to bond the paver to one, two, three, or four other perviousconcrete pavers or slabs. An example method of forming the paver 400 isdescribed in detail below in connection with FIG. 8.

The paver 400 is substantially similar to the first paver 102 and thesecond paver 104 described above. For example, the paver 400 includes afirst keyway 402 formed along a first edge 404 of a body 406 of thepaver 400, and a second keyway 408 formed along a second edge 410 of thebody 406 opposite the first edge 404. Additionally, a third keyway 412is formed along a third edge 414 of the body 406 of the paver 400, and afourth keyway 416 is formed along a fourth edge 418 of the body 406opposite the third edge 414. The first keyway 402, second keyway 408,third keyway 412, and fourth keyway 416 each have a thickness 420 thatis less than a maximum thickness 422 of the body 406. In the exampleshown, the respective keywords are approximately half the maximumthickness 422 of the body 406. Other embodiments are possible.

At least one channel 424 is formed within the body 406 between thefourth edge 418 and a notch 426 defined within the third keyway 412. Afirst beveled surface 428 is formed on a first channel end 430 of thechannel 424, and a second beveled surface 432 is formed on a secondchannel end 434 opposite the first channel end 430. Similar to theexamples described above, a strap coupled to a lifting mechanism ispositioned into the channel 424 to facilitate lifting and/or moving ofthe paver 400. The first beveled surface 428 and the second beveledsurface 432 provide stress relief to the strap and facilitate strapremoval when the paver 400 is in contact with the ground surface 106, orthe aggregate layer 110. The notch 426 further facilitates strap removalwhen the paver 400 is in contact with a ground surface. Otherembodiments are possible.

In some embodiments, the paver 400 includes chamfered or rounded cornersto protect the paver 400 from chipping or raveling when installed.Chamfered or rounded corners additionally provides for an aestheticallypleasing appearance. For example, respective edges 436, 438, 440, 442may be selectively chamfered or rounded (shown as intermittent lines inFIG. 5) either as part of the manufacturing process or prior toinstallation of the paver 400.

Referring now to FIG. 6, an example parking lot 600 of a store 602 isshown having a first installation site 604, a second installation site606, a third installation site 608, a fourth installation site 610, afifth installation site 612, and a sixth installation site 614. Inexample embodiments, the first installation site 604, secondinstallation site 606, third installation site 608, and fourthinstallation site 610 each include a water filtration systemsubstantially similar to the first example water filtration system 100described above in connection with FIG. 1-5.

The fifth installation site 612 and the sixth installation site 614 eachinclude a second example water filtration system 616 in accordance withthe present disclosure. FIG. 7 shows a cross-sectional view of thesecond example water filtration system 616 taken along a cross-sectionA′-A′ of the fifth installation site 612.

Specifically, FIG. 7 shows the second example water filtration system616 including a plurality of pervious concrete slabs 618 each at leastpartially positioned within a ground surface 620 of the fifthinstallation site 612. Each of the plurality of pervious concrete slabs618 are similar to one of the first paver 102, second paver 104, andpaver 400 as described above.

The water filtration system 616 also includes an aggregate layer 622positioned beneath the plurality of pervious concrete slabs 618, and asubgrade layer 624 positioned beneath the aggregate layer 622. In someembodiments, the water filtration system 616 further includes a firstand second fabric layer (not shown) positioned with respect to theplurality of pervious concrete slabs 618, aggregate layer 622, andsubgrade layer 624 similar to the first and second fabric layer 112, 116described above. Other embodiments are possible as well.

The water filtration system 616 further includes a pipe 626 coupled to astormwater drainage pipe 628. The pipe 626 extends through a sub-soillayer 630, subgrade layer 624, aggregate layer 622, and one or more ofthe plurality of pervious concrete slabs 618 to a catch basin 632defined within the ground surface 620. In the example embodiment, theplurality of pervious concrete slabs 618, aggregate layer 622, andsubgrade layer 624 are installed by the catch basin 632 to capture andfilter water that would otherwise be unfiltered and potentially pollutea lake, river, or ocean.

Baffles 634 are installed to the pipe 626 to release filtered water fromthe aggregate layer 622 into the stormwater drainage pipe 628. Thebaffles 634 additionally prevent the plurality of pervious concreteslabs 618 and the aggregate layer 622 from becoming saturated orsaturated then frozen, which would cause the water filtration system 616to generally fail. Additionally, weep lines 636 are installed to thepipe 626 to release filtered water from the subgrade layer 624 into thestormwater drainage pipe 628. In example embodiments, the weep lines 636are smaller in diameter than the baffles 634, and allow the aggregatelayer 622 to completely drain. This can be important in freeze-thawclimates, in which it is desirable to keep water moving continuouslythrough the aggregate layer 622 without freezing.

Referring now to FIG. 8, an example method 800 is shown for forming apre-cast pervious concrete slab for a water filtration system accordingto the principles of the present disclosure.

The method begins at a step 802. At step 802, a concrete mixture isformed comprising aggregate particles, hydraulic cement, and water. Incertain embodiments, one or more additives are also added to the mixtureat step 802. Example additives include a plasticizer, an air entrainmentagent, a strength enhancing agent or fiber, calcium chloride, coloringagent, a water reducer, and a retarder. In general, type and quantitiesof materials added to the concrete mixture are selectable based ondesired properties of the final product.

One example concrete mixture includes: 0.5 cubic feet of ⅜″ aggregate; 4gallons of Portland cement; 192 ounces of water; 1 ounce of an airentrainment agent; and 1 ounce of plasticizer. One example mixing orderof the ingredients of the example mixture includes: (1) add 0.25 cubicfeet of ⅜″ aggregate; (2) add 2 gallons of Portland cement; (3) add 0.25cubic feet of ⅜″ aggregate; (4) add 2 gallons of Portland cement; (5)add 64 ounces of water; (6) add 1 ounce of an air entrainment agent; (7)and 1 ounce of plasticizer (if needed).

Other embodiments of forming the concrete mixture at step 802 arepossible.

Process flow proceeds to a step 804. At step 804, the concrete mixtureis poured into a mold, vibrated for a first predetermined time period,and then compressed for a second predetermined time period. In oneembodiment, a frequency of the vibration is in a range of about 10 Hertzto about 1000 Hertz, and a pressure of the compression is in a range ofabout 10 pounds per square inch to about 1000 pounds per square inch.Other embodiments are possible.

Process flow proceeds to a step 806. At step 806, the pervious concreteslab is released from the mold and transferred to a holding area havinga controlled ambient environment. In one embodiment, the perviousconcrete slab includes an interconnected void content of about 10% toabout 30%. In general, the void content is dependent on processparameters including, but not limited to, aggregate size, compressionand vibration of the concrete mixture when positioned within the mold,and others. The pervious concrete slab is then cured for a thirdpredetermined time period by misting water into the controlled ambientenvironment. Process flow then proceeds to a step 808. At step 808, thepervious concrete slab is transferred to an installation site of thewater filtration system.

The example method 800 is advantageous in many aspects. For example,reproducible, high quality material is achieved by casting perviousconcrete pieces in a quality controlled environment, prior to shippingcorresponding pieces to an installation site. Additionally, onceinstalled and incorporated within a water filtration and/or recyclingsystem, contaminant(s) may be prevented from reaching lakes, rivers,streams, ground water, etc. Furthermore, the pervious concrete piecescan be defined to have any geometry as desired (e.g., circular,polygonal, etc.) and any number of keyways as desired (e.g., three-sidedkeyway system, five-sided keyway system, etc.).

Although the subject matter of the present disclosure has been describedin language specific to structural features and/or methodological acts,it is to be understood that the subject matter defined in the appendedclaims is not necessarily limited to the specific features or actsdescribed above. Rather, the specific features and acts described aboveare disclosed as example forms of implementing the claims.

1. A pre-cast pervious concrete slab formed in a mold through vibrationand compression, the pre-cast pervious concrete slab, comprising: a bodyhaving opposite first and second side edges and opposite third andfourth side edges, the body being composed of a combination of aggregateparticles, cementitious materials, and water, and wherein the bodyincludes an interconnected void content of about 10% to about 30%; alifting feature for allowing the slab body to be lifted, the liftingfeature being integrated into the slab body and extending continuouslybetween two of the first, second, third, and fourth side edges; and analignment feature for aligning the slab body with another pre-castpervious concrete slab, the alignment feature being located at one ofthe first, second, third, and fourth side edges.
 2. The pre-castpervious concrete slab of claim 1, wherein the aggregate particlescomprise an average particle size of about 9.5 millimeters.
 3. Thepre-cast pervious concrete slab of claim 1, wherein the cementitiousmaterials comprise a hydraulic cement.
 4. The pre-cast pervious concreteslab of claim 1, wherein the body is further composed of one or moreadditives selected from the group including: plasticizer; airentrainment agent; strength enhancing agent or fiber; calcium chloride;coloring agent; water reducer; and retarder.
 5. The pre-cast perviousconcrete slab of claim 1, wherein the alignment feature is integral tothe body and includes at least a first edge structure extending alongthe first edge of the body and a second edge structure extending alongthe second edge of the body, the first and second edge structures havingcooperatively fitting profiles, each of the first and second edgestructures being defined by a cross-sectional area that is less than amaximum cross-sectional area of the body.
 6. The pre-cast perviousconcrete slab of claim 5, wherein the first edge structure and secondedge structure each have a thickness about half the maximum thickness ofthe body.
 7. The pre-cast pervious concrete slab of claim 6, wherein themaximum thickness of the body is in a range of about 50 millimeters toabout 406 millimeters.
 8. The pre-cast pervious concrete slab of claim1, wherein the lifting feature includes a channel formed between thethird and fourth opposite edges of the body.
 9. The pre-cast perviousconcrete slab of claim 8, wherein first and second beveled edges areformed on opposite ends of the channel.
 10. A water filtration system,comprising: a plurality of pervious concrete pavers, each composed of acombination of aggregate particles, cementitious materials, and water,and including a void content of about 10% to about 30%; and a filtrationlayer positioned beneath the plurality of pervious concrete paverswithin the ground surface.
 11. The water filtration system of claim 10,wherein each of the plurality of pervious concrete pavers are furthercomposed of one or more additives selected from the group including:plasticizer; air entrainment agent; strength enhancing agent or fiber;calcium chloride; coloring agent; water reducer; and retarder.
 12. Thewater filtration system of claim 10, further comprising a subgrade layerpositioned beneath the filtration layer within the ground surface. 13.The water filtration system of claim 12, further comprising at least oneof: a first filter fabric positioned between the filtration layer andthe subgrade layer; and a second filter fabric positioned beneath thesubgrade layer and at least adjacent to portions of the filtration layerand the subgrade layer within the ground surface.
 14. The waterfiltration system of claim 12, further comprising: a perforated pipepositioned beneath the subgrade layer, wherein the perforated pipe iscoupled to a first non-perforated pipe that is coupled to a liquidcontainer positioned within the ground surface; and a secondnon-perforated pipe that is coupled to the liquid container and a waterdisbursement mechanism at least partially positioned above the groundsurface.
 15. The water filtration system of claim 10, wherein theaggregate particles comprise an average particle size of about 9.5millimeters and the cementitious materials comprise a hydraulic cement.16. The water filtration system of claim 10, wherein each of theplurality of pervious pavers further include at least a first and secondkeyway formed along first and second opposite edges of a correspondingpaver, the first keyway and second keyway each defined by a thicknessthat is less than a maximum paver thickness
 17. The water filtrationsystem of claim 10, wherein each of the plurality of pervious paversinclude at least one channel formed between third and fourth oppositeedges of a corresponding paver, and wherein first and second bevelededges are formed on opposite ends of the at least one channel.
 18. Amethod of forming a pre-cast pervious concrete slab for a waterfiltration system, comprising: forming a mixture comprising aggregateparticles, hydraulic cement, and water; pouring the mixture into a moldto define the pervious concrete slab; vibrating the mixture within themold for a first predetermined time period, wherein a frequency of thevibration is in a range of about 10 Hz to about 1000 Hz; compressing themixture within the mold for a second predetermined time period, whereina pressure of the compression is in a range of about 10 psi to about1000 psi; and releasing the pervious concrete slab from the moldfollowing the second predetermined time period.
 19. The method of claim18, further comprising: transferring the pervious concrete slab to aholding area having a controlled ambient environment following releaseof the pervious concrete slab from the mold; curing the perviousconcrete slab for a third predetermined time period by misting waterinto the controlled ambient environment; and transferring the perviousconcrete slab to an installation site of the water filtration systemfollowing release from the mold.
 20. The method of claim 18, whereinforming the mixture further comprises adding one or more materialsselected from the group including: plasticizer; air entrainment agent;strength enhancing agent or fiber; calcium chloride; coloring agent;water reducer; and retarder.